Journal of Thermal Spray Technology

, Volume 27, Issue 3, pp 423–432 | Cite as

Novel Online Diagnostic Analysis for In-Flight Particle Properties in Cold Spraying

  • Heli Koivuluoto
  • Ville Matikainen
  • Jussi Larjo
  • Petri Vuoristo
Peer Reviewed


In cold spraying, powder particles are accelerated by preheated supersonic gas stream to high velocities and sprayed on a substrate. The particle velocities depend on the equipment design and process parameters, e.g., on the type of the process gas and its pressure and temperature. These, in turn, affect the coating structure and the properties. The particle velocities in cold spraying are high, and the particle temperatures are low, which can, therefore, be a challenge for the diagnostic methods. A novel optical online diagnostic system, HiWatch HR, will open new possibilities for measuring particle in-flight properties in cold spray processes. The system employs an imaging measurement technique called S-PTV (sizing-particle tracking velocimetry), first introduced in this research. This technique enables an accurate particle size measurement also for small diameter particles with a large powder volume. The aim of this study was to evaluate the velocities of metallic particles sprayed with HPCS and LPCS systems and with varying process parameters. The measured in-flight particle properties were further linked to the resulting coating properties. Furthermore, the camera was able to provide information about variations during the spraying, e.g., fluctuating powder feeding, which is important from the process control and quality control point of view.


cold spraying diagnostics in-flight properties particle size particle velocity 



The work has been done within DIMECC Ltd. and its HYBRIDS program. The authors gratefully acknowledge the financial support from Tekes (Finnish Funding Agency for Technology and Innovation) and the participating companies. Also, the authors would like to thank Mr. Mikko Kylmälahti, of Tampere University of Technology, for spraying experiments and M.Sc. Juha Lagerbom, of VTT (Finland), for measuring particle size distributions by laser diffraction technique.


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Copyright information

© ASM International 2018

Authors and Affiliations

  • Heli Koivuluoto
    • 1
  • Ville Matikainen
    • 1
  • Jussi Larjo
    • 2
  • Petri Vuoristo
    • 1
  1. 1.Laboratory of Materials ScienceTampere University of TechnologyTampereFinland
  2. 2.Oseir LtdTampereFinland

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